FEEDBACK TECHNIQUE FOR WIRELESS SYSTEMS WITH MULTIPLE TRANSMIT AND RECEIVE ANTENNAS

摘要

In a wireless communication system using multiple antennas at the transmitt er and multiple antennas at the receiver, a so called multiple-input multiple- output (MIMO) system, a substantial improvement in capacity over the case of no feedback can be achieved using considerably less bandwidth than is required to feedba ck the channel estimate or channel statistics, by supplying as feedback for each da ta substream of an overall data stream an indicator of a rate and/or an indicat or of a gain for transmission of that data substream. The indicator of the rate and/or th e indicator of the gain may be the rate and/or gain directly or an encoded representatio n of the rate and/or gain. Typically, the best performance is achieved if indicators of both the rate and the gain are fed back. If the invention is implemented for wireless systems, then typically for each data substream there is a separate, independent antenna. The rate and the gain are computed as a function of a channel estimate which is developed at the receiver. Advantageously, the transmitter may employ only one- dimensional data coding for each of the data substreams.